Even though the amount of plastics used in a variety of consumer goods, packaging and medical articles has not increased over the past twenty years, the visual perception is that more and more nondegradable plastics are filling up our landfills. Plastics offer many advantages over the more traditional wood, glass, paper, and metal articles including improved performance, comparable or decreased cost of manufacture, decreased transportation costs, etc. Disposal of all waste materials including food waste, packaging materials, etc. into a typical landfill provides a relatively stable environment in which none of these is seen to decompose at an appreciable rate. Alternative waste disposal options are increasingly discussed and utilized to divert some fractions of waste from entombment. Examples of these alternatives include municipal solid waste composting, anaerobic digestion, enzymatic digestion, and waste water sewage treatment.
Developing compositions and articles which are more compatible with these waste disposal methods is a goal professed in the current art of plastics improvements.
The art has previously recognized a variety of articles designed for disposal into the toilet or water closet after use, commonly termed "flushable." Flushable articles could, but do not always, totally disperse within the waste water system. They are principally constructed to avoid clogging the waste water system. Nonwoven articles of this type are typically useful for feminine hygiene or incontinence. For example, the disposable sanitary products described in U.S. Pat. No. 3,480,016 are comprised of fibers bound together by a resin which is insoluble in water but will disperse due to water sensitivity upon disposal into the toilet. Similar structures are claimed in U.S. Pat. No. 3,804,092. Alternatively, composite flushable structures for feminine hygiene articles include those described in PCT Publication WO 91/08726 wherein an absorbent core of fibrous material is laminated to a water permeable topsheet and a water impermeable backsheet. The topsheet may be a film or a nonwoven and both the topsheet and backsheet were described as comprising polylactide or polyglycolide. Similar composite articles and uses are described by U.S. Pat. No. 5,300,358.
There exists art describing a variety of flushable articles comprised of film structures. For example, a bedpan liner was described in U.S. Pat. No. 3,546,716 which is made from a cold water soluble base film, e.g. poly(vinyl alcohol) film, coated with a water insoluble or water repellent material. The structures also contain a tissue paper covering adhered to the water insoluble coating and the preferred disposal is into the sewage system.
Another series of articles designed to be flushed into sewage treatment is described by U.S. Pat. No. 4,372,311 wherein disposable articles comprised of water soluble films coated with an insoluble material are claimed. Articles may be useful as feminine hygiene products, diaper components, or bandages. The existence of a laminate structure was noted, this being that when the coating was of sufficient thickness to have film-like properties unto itself.
The use of a water soluble film coated with or laminated to a water insoluble film as a disposable bag is described in U.S. Pat. No. 4,620,999. The claims describe a package for body waste which is stable to human waste during use but which can be made to degrade in the toilet at a rate suitable for entry into a sewage system without blockage by adding a caustic substance to achieve a pH of at least about 12. Such structures are typically a poly(vinyl alcohol) film layer coated with poly(hydroxybutryate).
A related structure is described by PCT Publication WO 92/01556. A multilayer film containing layers of water insoluble and water soluble films is described, where both layers may be made from poly(vinyl alcohol) and a difference in the extent of hydrolysis provides the differential solubility. The mechanical strength of the composite comes from the water soluble component and the resistance from water during use is derived from the water insoluble coating. Uses envisioned included diapers, cups, golf tees, and laundry bags. A later publication WO 93/22125 describes the process for making these structures and lists additional article claims for sanitary articles and articles where the insoluble coating is specifically an ink.
Compositions comprised of multilayer films are known in the art. The utility of such structures lies in the manipulation of physical properties in order to increase the stability or lifetime during use of such a structure. For example, U.S. Pat. Nos. 4,826,493 and 4,880,592 describe the use of a thin layer of hydroxybutyrate polymer as a component of a multilayer structure as a barrier film for diaper components and ostomy bags.
Others have designed multilayer films specifically to be compostable. PCT Publication WO 92/15454 describes films which are comprised of external layers of an environmentally degradable film and an internal layer of a biodegradable, water soluble film. Typically, the external layers are comprised of a polyolefin, poly(caprolactone), or ethylene vinyl acetate and the internal layer is described as poly(vinyl alcohol). One of the external layers may be a nonwoven structure. Additional art in this area is described by EPO Publication 0 616 570.
The development of a multilayer microfiber has been noted in the art. Basic technology building patents describing the process by which multilayer microfibers can be prepared are described in U.S. Pat. No. 5,207,970.
Disposal of medical waste is increasingly coming under the scrutiny of government agencies and the public alike. Concerns over the fate of materials contaminated with infectious substances are valid and proper measures to insure the safety of health care workers and the general public should be taken.
Currently, medical waste can be categorized into reusable and disposable. Reusable medical articles are cleansed and sterilized under stringent conditions to ensure disinfection. For example, reusable medical devices such as garments or drapes can be used up to 100 times. In comparison, after use, disposable medical articles are typically disinfected or sterilized, adding a significant cost, prior to disposal into a specially designated landfill or waste incinerator. Often, the disposal cost for the contaminated single use articles is quite high.
The utility of a water dispersible tape for use on reusable surgical drapes and gowns was recognized in U.S. Pat. Nos. 5,125,995 and 5,270,111. The use of a water dispersible indicator tape was recognized in PCT Publication WO 93/24152.
Furthermore, a series of U.S. Patents describes composite fabrics, utensils, packaging materials and a method for disposing garments and fabrics which are soluble in hot water, namely: U.S. Pat. Nos. 5,268,222; 5,207,827; 5,181,967; and 5,181,966. The structures described are typically comprised principally of poly(vinyl alcohol) which is only soluble above 37.degree. C. The target disposal method for said articles is via laundering where the temperature is usually greater than 50.degree. C.
Similar fabrics are described in Canadian Patent Publication 2,093,051. A composite structure of nonwoven layers is prepared from a poly(vinyl alcohol) component and another material which acts as a barrier layer during use. The nonwoven fabrics claimed are designed to disperse in an aqueous environment having a pH greater than 12 and a temperature greater than 70.degree. C. in a period of less than about 10 minutes.
Generally, poly(lactic acid), its blends and several articles made thereof are described in U.S. Pat. Nos. 5,200,247; 5,227,415; 5,076,983; 5,216,050; 5,359,026; and PCT Publications WO 94/06866; WO 94/07941; WO 94/08078; WO 92/04412; and WO 92/04410 and references cited therein. No references to the utility of poly(lactic acid) in a laundry dispersible article were described.
Poly(ester amide)s are described in a series of patents by Barrows, et.al. in U.S. Pat. Nos. 5,286,837; 4,529,792; and 4,343,931. The utility of such materials in a laundry dispersible article was not realized.